Table of Allowed Domains

Is it possible to configure the open source edition of Zimbra to restrict sending and receiving email only to certain domains? Ideally it would be a table of allowed domains, and outgoing or incoming mail to other domains would be rejected. I am considering Zimbra to replace our current email server which we have configured in this way, for secure communication only within our organization. Also, can Zimbra be configured for alternate ports for pop3 and smtp services?

Thank you, that is very helpful. But does the whitelist take priority over the blacklist, that is, can I deny all domains in the blacklist with "*@*.*" and then allow specific domains in the whitelist with "*@mydomain.com"?